With the rapid development of capture equipments, storage technologies and the growing needs for better visual experience from the viewer, high bit-rate video has already been applied widely for content distribution, movie production and video broadcasting. Moreover, in the next coming years, high bit-rate videos will be available not only for professional content providers, but also for consumers.
Video equipment such as non-linear editing systems, e.g. for TV production studios, may need to display multiple channels of bit-streams in real-time simultaneously. Decoding multiple streams of high bit-rate videos is extremely computational intensive. Prior art1 to solve this issue with software need an auxiliary file to store less frequency coefficients and a partial additional stream, and yields just a blurry version of the video. However, to store such auxiliary file for each bit-stream takes much time and storage space. It is a preprocessing technique that requires off-line computation, therefore it is impossible to browse an MPEG-1/2 bit-stream in real-time. Moreover, using a fixed scheme of only DC values or only DC+2AC values is inflexible and cannot make full use of the available resources. Decoding of one or multiple high bit-rate video streams with hardware is very expensive because multiple sets of hardware are required for decoding multiple video channels. 1J. Song and Boon-Lock Yeo, “Fast Extraction of Spatially Reduced Image Sequences from MPEG-2 Compressed Video”, IEEE Transaction on Circuit and System For Video Technology, Vol. 9, No. 7, October 1999, pp 1100-1114
The normal frame-rate for video in television is usually 24 or 30 frames per second (fps). But nowadays, since the growing requirement of customers, higher frame-rate videos are becoming popular in video content production and even TV broadcasting. Higher frame-rates can e.g. avoid motion blur caused by the display mechanism of LCD displays; therefore more pleasing visual effects can be offered. Also in professional video applications, such as TV program production and movie content distribution, high frame-rate is often chosen to ensure the viewer gets the best visual experience.
However, the higher the frame rate is, the more complex the decoding process will be. Therefore real-time decoding of one or multiple channels with high frame-rate video is a challenge. Existing solutions for the frame-rate pull down process employ a brute force method: a target output frame-rate is provided, and then each xth frame is dropped, in an equidistant manner, to control the resulting frame-rate. Therefore, the subjective quality of the decoded video can become very low. Especially when the input frame-rate varies a lot from the output frame-rate, there will be a lot of motion jerkiness and annoying artifacts. It is therefore desirable to find a solution for fast real-time video browsing with improved visual quality, e.g. by an improved frame-rate pull down method.